YuanNa LiThe file of manuscript.docx

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Themaintenanceofthesecond-orderadvantage:

Second-ordercalibrationofexcitation-emissionmatrixfluorescenceforquantitativeanalysisofherbicidenapropamideinvariousenvironmentalsamples

Yuan-NaLi,Hai-LongWu*,Xiang-DongQing,Chong-ChongNie,Shu-FangLi,Yong-JieYu,Shu-RongZhangandRu-QinYu

StateKeyLaboratoryofChemo/BiosensingandChemometrics,CollegeofChemistryandChemicalEngineering,HunanUniversity,Changsha410082,PRChina

Correspondingauthor.Tel.:

+86-731-88821818.

Fax:

+86-731-88821818.

E-mailaddress:

hlwu@（H.-L.WU）.

Abstract

Arapidnon-separativespectrofluorometricmethodbasedonthesecond-ordercalibrationofexcitation-emissionmatrix（EEM）fluorescencewasproposedforthedeterminationofnapropamide（NAP）insoil,riversediment,andwastewateraswellasriverwatersamples.With0.10molL-1sodiumcitrate-hydrochloricacid（HCl）buffersolutionofpH2.2,thesystemofNAPhasalargeincreaseinfluorescenceintensity.Tohandletheintrinsicfluorescenceinterferencesofenvironmentalsamples,thealternatingpenaltytrilineardecomposition（APTLD）algorithmasanefficientthree-waycalibrationmethodwasemployed.SatisfactoryresultshavebeenachievedforNAPincomplexenvironmentalsamples.ThelimitofdetectionobtainedforNAPinsoil,riversediment,wastewaterandriverwatersampleswere0.80,0.24,0.12,0.071ngmL-1,respectively.Furthermore,inordertofullyinvestigatetheperformanceofsecond-ordercalibrationmethod,wetestthesecond-ordercalibrationmethodusingdifferentcalibrationapproachesincludingthesinglematrixmodel,thedailyvariousmatricesmodelandtheglobalmodelbasedontheAPTLDalgorithmwithnatureenvironmentaldatasets.Theresultsshowedthesecond-ordercalibrationmethodsalsoenableoneormoreanalytesofinteresttobedeterminedinvariousmatricessimultaneously.Themaintenanceofsecond-orderadvantagehasbeendemonstratedinvariousmatricesdecompositionsimultaneously.

Keywords:

second-ordercalibration;napropamide;APTLD;excitation-emissionmatrixfluorescence;calibrationmaintenance

1.Introduction

Withthedevelopmentofmodernsecond-orderinstrumentswhichgeneratealotofsecond-orderdata,second-ordercalibrationmethodsaregainingwidespreadacceptancebytheanalyticalcommunity.Second-ordercalibrationallowsconcentrationsandspectralprofilesofthesamplecomponentstobeextractedinthepresenceofanynumberofunexpectedconstituents[1-4].Thisproperty,namedthe“second-orderadvantage”,isespeciallyconvenientwhenanalystshandlecomplexmatrices.Inrecentdecades,agreatvarietyofsecond-ordercalibrationmethodshavebeenproducedforathree-waydataarray,suchasparallelfactoranalysis（PARAFAC）[5,6],generalizedrankannihilationmethod（GRAM）[7],multivariatecurveresolution-alternatingleastsquares（MCR-ALS）[8],alternatingtrilineardecomposition（ATLD）[9],self-weighedalternatingtrilineardecomposition（SWATLD）[10]andalternatingpenaltytrilineardecomposition（APTLD）[11].Takingintoadvantageoftheproperty,itenablesseveralanalytesofinteresttobedeterminedsimultaneouslyinonesetofmatrixsamples,whichhasbeendemonstratedandappliedinmanyanalyticalfields[12-16],e.g.,pharmaceuticals,biologicalmatrices,foods,environmentalmatricesandsynthetic;Ontheotherhand,italsoenablesoneormoreanalytesofinteresttobedeterminedinvariousmatrixsamplessimultaneously,thereareafewapplicationsinthisaspect.Testosteronepropionatewasdeterminedinseveralcosmeticsusingexcitation-emissionmatrixfluorescencewiththeaidofsecond-ordercalibrationmethods[17].

Themaintenanceofsecond-orderadvantagefromdaytodayorinvariousdifferentmatricesisaninterestingproblemwhenananalyticalmethodisproposedforrapidroutinedailyuse.ThePARAFACmodelappliedtoexcitation-emissionmatrix（EEMs）fluorescencesignalsandthroughtheglobalmodelstrategyhasbeenprovedusefultopredictaccuratelysamplesmeasuredondifferentdays,bydifferentanalystsandeveninthepresenceofnon-modelledinterferentsbyGiménezetal[18].Inaddition,thepredictionqualityofsecond-ordercalibrationasafunctionofthesizeofthecalibrationset,thenumberanddegreeofoverlapofnewinterferentsandthetypeandmagnitudeofnoisewasinvestigatedbyRinnan[19],andtheguidelinesweregivenonhowtoimplementpredictionsinPARAFAC-basedsecond-ordercalibration.However,therehasnotbeenmuchworkonthecomparisonofpredictionqualityforthesinglematrixmodel（thecalibrationsetcombinedwithone-matrixsamples）,thedailyvariousmatrixmodel（thecalibrationsetcombinedwithdifferentmatrixintra-daydata）andtheglobal（inter-dailyvariousmatrices）model（twocalibrationsetscombinedwithdifferentmatrices）.Themaintenanceofthesecond-orderadvantagehasnotbeenfullydemonstratedoneormoreanalyte（s）ofinterestaredeterminedinvariousdifferentmatrices.

Herbicidesarechemicalsoftenemployedtokillweedswithoutcausinginjurytodesirablevegetation.Napropamide[N,N-diethyl-2-（1-naphthalenyloxy）propanamide],isahighlyeffectivebroad-spectrumamideherbicideandwidelyusedaspre-emergenceherbicideweedingoutmostannualmonocotyledonandbroadleafweedsinmanyagriculturalcultivations,suchastea,groundnut,citrus,tobacco,andtomatoesetc[20].However,thetoxicityofthisherbicidehasbeenstudied,whichshowedthatinhalation,contactwitheyes,skinandclothingandprolongedandrepeatedexposuremustbeavoided[21].Furthermore,duetoitslonghalf-life（approximate70days）,theresidueofnapropamideinsoilsmayaffectthegrowthofsucceedingcrops.Besides,itspropertyofmoderateadsorption/desorptiononsoilsalsomakesnapropamidefairlymobileandleaching,thusresultingincontaminationofwastewater,riversandriversediments[22].Therefore,itshighuseonagrarianactivityresultedinincreasingneedforsensitiveanalyticalmethodsfornapropamidedeterminationindifferentmatrixes,suchassoil,wastewater,riverwater,andriversediments.

Owingtoitsintrinsicsensitivity,easinessofuse,andavailabilityofinstruments,fluorescencespectroscopyprovidesavaluabletooltoanalyticalchemists.Nevertheless,fluorescencesignalpeakofsubstanceisusuallybroad,soincomplexmixturesthesignalwillbeoverlapped.Moreover,whenagivensamplecarriesunexpectedfluorescentconstituentsthathavenotbeenmodeledduringthecalibrationphase,aconvenientwayofquantifyinganalytesofinterestincomplexmixturesisbyresortingtohigher-orderdatacoupledtothesecond-orderadvantage.Thestructureofnapropamide（Fig.1）hasanaphthalenering,whichconnectswithaconjugatedoublebondsystem;itcangiveoffstrongfluorescenceinproperconditions[23].So,inthispaper,wehaveattemptedtomakeuseofexcitation-emissionmatrix（EEMs）fluorescencetoestimateherbicidenapropamideinvariousenvironmentalsampleswiththeaidofsecond-ordercalibrationmethod.

[Fig.1]

Inthepresentstudy,wedevelopedarapidandsensitivenon-separativeexcitation-emissionfluorescencemethodforthedeterminationofherbicidenapropamideinsoil,riversediment,wastewaterandriverwatersamplesusingtheAPTLDalgorithmasasecond-ordercalibrationmethod.Thefiguresofmeritinvolvingsensitivity（SEN）,selectivity（SEL）andlimitofdetection（LOD）,aswellasthelimitofquantification（LOQ）wereinvestigated.Inaddition,acomparisonofpredictionqualitiesamongthesinglematrixmodel,thedailymatrixmodelandtheglobalmodelintheAPTLDalgorithm-basedsecond-ordercalibrationhasbeendoneinthiswork.

2.Experimental

2.1Reagentsandchemicals

Allreagentsandchemicalsusedwereofanalyticalreagentgrade.Napropamide（NAP）（purchasedfromDr.EhrenstorferCorporation,Germany,content>99.5%）wasusedwithoutfurtherpurification.Allglasswareswerepreviouslysoakedinchromatelotionovernight,andthenrinsedwithultrapure-gradewaterpriortotheuse.Astocksolutionof50.0μgmL-1waspreparedbyaccuratelyweighingtherequiredamountsofNAPanddissolvinginacetonitrileanddilutingwithultrapure-gradewaterina100mLbrownvolumetricflask,andthenstoredat4℃inarefrigeratoruntilused.TheworkingsolutionsofNAPweredailypreparedbydilutingthestocksolutionswithultrapure-gradewater.The0.10molL-1sodiumcitrate-hydrochloricacid（HCl）buffersolutionofpH2.2wasprepared.

2.2Instrumentationandsoftware

AllofthefluorescencemeasurementswereperformedonanF-4500fluorescentspectrophotometer（Hitachi,Japan）,whichwasequippedwithacontinuous150-Wxenonarclampandinterfacedtoapersonalcomputer.Inallcases,a1.00cmquartzcellwasusedatroomtemperature.IntheMATLABenvironmentallhome-madeprogramswerewrittenandfurtherusedfordataanalysis.AllcalculationswerecarriedoutonamicrocomputerundertheWindowsXPoperatingsystem.

Allofthespectralsurfaceswererecordedatexcitationwavelengthsvaryingfrom250to310nmin2nmsteps,andemissionwavelengthsvaryingfrom320to396nmin2nmstepswithascanningrateof1200nmmin-1.Forasinglesample,amatrixofsizeof39×31wasobtained.Theusedspectralrangeswereselectedafterasuitableconsiderationofthespectralregionscorrespondingtomaximumsignalsfortheanalyteandavoidinguselessbackgroundsignals,suchasRayleighandRomanscatterings.Theslitwidthwas5.0/5.0nm.

2.3Environmentalsamplecollectionandpreparation

ThesoilsamplesandriversedimentsampleswerecollectedfromthecroplandandthebankoftheXiangjiangRiverinHunan